Roof tile



March 21, 1939.- R. A PLUME', 2,151,148

ROOF TILE Filed March 3, v1938 2 Sheets-Sheet l @2, Y a? 130 l www March21, 1939K.. R A, PLUME 2,151,148

ROOF TILE Filed Mar-Ch 5, 1938 2 Sheets-Sheet 2 420 49 4.? A! ya ,4.9/2a1 f ff sa d' fr. 48]

L l s l E if /N VENTOR Patented Mar. 21, 1939 UNITED STATES ROOF TILERoy A. Plumb, Pleasant Ridge, Mich., assignor to The TrusconLaboratories, a corporation of Michigan Application March 3, 1938,Serial No. 193,685

16 Claims.

This invention relates to composite factory fabricated building unitsand in particular to insulated load supporting building units adaptedfor use as roof tile which also may be employed v advantageously infloor andwall construction.

The roofs of buildings are ordinarily constructed of suitable loadsupporting members such as ywood plank, concrete slabs, steel tile,concrete tile, or other material presenting a hard surface over which awater proof roofing material is placed, the said wood plank, concreteslabs, steel tile, concrete tile or the like being supported on beams orpurlins spaced at suitable intervals usually from four. to eight feet oncenter which in turn are supported on roof girders or trusses, allaccording to the particular design of the roof structure. In order toavoid heat losses through the roof construction from within the buildingduring the lwinter months and to prevent the admission of heat from thesuns rays during the summer months, a layer of insulation such as corkboard or sheets of brous cellular material is generally used as heatinsulation and placed between the supported roof surface and thewaterproof roofing material placed thereon.

It is readily observed that notonly does it require three operations tocomplete an insulated roof, namely, the construction of the structuralroof, the placing of insulating material thereover, 30, and the placingof the waterproof roofing on the said insulating material, but, becauseof the cellular fibrous nature of various insulating materials generallyemployed over the structural roof surface, the construction of a roofcannot proceed during damp, rainy or snowy weather because of theharmful saturation of the various types of insulating materials employedduring the laying of the insulating material and before the waterproofroofing is placed thereover. Also, it is expensive to handle the varioustypes of fibrous insulating material generally employed as roofinsulation on or about a construction job because it must be stored offthe ground to avoid saturation by capillary attraction and because itmust be covered to avoid saturation from moisture in the air, rain orsnow.

Because of the fact that the various types of fibrous insulatingmaterials generally employed to insulate roofs contain many voids andare subject to being easily dented when concentrated loads are placedthereon, it is obvious that waterproof roofing placed thereover iscontinually subject to being dented, punctured and otherwise 5 harmed bywalkingthereover, the placing of conf centrated loads thereon and byother traffic to which roofs are generally subjected.

It is not desirable to use wood plank for roof construction because ofthe fire hazard thereof; poured concrete roof slabs are extremelyexpensive because of the necessary forming therefor and the timerequired for the setting thereof; steel roof tile becomes twisted,dented and otherwise bent out of shape during shipping and erection; andconcrete roof tile is easily broken, chipped or cracked during shipmentand erection and is costly to erect because of its weight in comparisonto the wood plank and steel tile for which it is generally substituted.

With the foregoing in view, the main object of this invention is toprovide a unitary factory fabricated roof tile which carries its owninsulation and provides the economy of eliminating the usual separateeld operation of placing roof insulation after the erection of the usualstructural roof surface and before the laying of the Waterproof roongthereover.

Another object of the invention is to provide a factory fabricatedinsulated roof tile unit capable of resisting weather during shipmentand cor1- struction whereby to admit of its use under all weatherconditions and thereby eliminate the necessity of holding up theconstruction of a roof during damp, rainy and snowy weather asheretofore required to avoid harmful saturation of the various types ofcellular and fibrous insulating material generally employed over thestructural roof and below the waterproof roofing.

Another object of the invention is to provide a unitary factoryfabricated insulation carrying roof tile having a metal'base and sideswhich serve as a form during manufacture of the same and which provide ahardened cementitious weather protection over the insulating materialemployed therein.

Another object of the invention is to provide a composite insulationcarrying roof tile having a metal base and sides and a topping ofreinforced cementitious material fabricated in such a manner as to causethe metal base and sides and the reinforced topping of cementitiousmaterial of the said composite tile to act together as a unitary wholeto provide resistance against compressive, flexural and shearingstresses to which the said roof tile may be subjected.

Another object of the invention is to provide a composite insulationcarrying roof tile having a metal base and sides and a topping ofreinforced cementitious material fabricated in such a manner as to causethe metal base and sides and the reinforced topping of cementitiousmaterial of the said composite tile to act together as a unitary wholeto provide resistance against compressive, flexural and shearingstresses to which the said roof tile may be subjected without any loadbeing carried by the insulation material employed therein.

Another object of the invention is to provide a complete unitarycomposite insulation carrying roof tile unit having a metal base andsides and topping of cementitious material fabricated and reinforced toact together as a unitary whole in resisting flexural stresses, which iscapable of being stored and erected in all types of weather Withoutharmful effects to the insulation thereof,

and which is capable of supplying the long wanted' demand for a roofingunit which is substantially free from breakage during shipping, handlingand erection.

Another object of this invention is to provide a'composite roof tilecomposed of a metal base and sides, suitable insulation material, and areinforced cementitious topping, the said tile having a high insulationvalue and which is so constructed as to protect the insulation thereofduring erection and the placing of roofing thereover, beingsubstantially free from breakage during shipment and erection, and whichis capable of acting as a unitary whole in resisting compressive andilexural stresses Without subjecting the insulation thereof to resistany stress whatsoever.

Other objects of the invention will become apparent by reference to thefollowing detailed description taken in connection with the accompanyingdrawings, in which:

Fig. 1 is a fragmentary side elevational view of a roof tile embodyingthe invention supported on roof beams or purlins.

Fig. 2 is a fragmentary plan view of the roof tile Y shown in Fig. 1with portions thereof broken away to better show the. invention.

Fig. 3 is an enlarged fragmentary'longitudinal` view taken on the line 33 of Fig. 2.

Fig. 4 is an enlarged cross sectional view taken on the line 4-4 of Fig.2.

Fig. 5 is a fragmentary cross sectional View similar to Fig. 4 showinghow the reinforcement of the cementitious topping of the roof tiledisclosed in Figs. 1 to 4 inclusive may be bonded to the metal sidesthereof without welding.

Fig. 6 is a fragmentary side elevational view of the modified form ofthe invention shown in Fig. 5.

' Fig. 7 is an enlarged cross sectional view similar to Fig. 5 showinghow the insulation of the roof tile disclosed in Figs. 1 to 6 inclusivemay be formed along the sides of the tile to provide additionalcementitious material at the sides to resist vertical and horizontalshearing stresses when the said tile is used on long spans or to supportheavy loads. Y

' Fig. 8 is an enlarged cross sectional view showing another embodimentof the invention in which none of the cementitious topping extendsaround the sides of the insulation therein.

Fig. 9 is a fragmentary elevational view of the embodiment of theinvention disclosed in Fig. 8.

Fig. 10 is a fragmentary side elevational view of still anotherembodiment of the invention.

Fig. 11 is a fragmentary plan View of the construction disclosed in Fig.l0 with certain portions thereof broken away to better illustratetheinvention. Y n

Fig. 12 is an enlarged fragmentary longitudinal View taken on thelineI2-l2 of Fig. 11.

Fig. 13 is an enlarged cross sectional view taken on the line l3-l3 ofFig. 11.

Referring now to the drawings wherein like numerals refer to like andcorresponding parts throughout the several views, the composite rooftile 23 disclosed in Figs. 1 to 7 inclusive and shown supported on roofbeams or purlins 2l in Fig. 1

is composed, in general, of a metal base 22 with f 4 vertically disposedsides 23 and 24 preferably Y a mesh or other suitable reinforcement 23for the said topping 2l preferably welded to or supported from the upperportion of the vertically disposed sides 23 and 24 in a manner similarto the construction shown in Figs. 4 and 5. Y

The sides 23 and 24 of the embodiment of the invention disclosed inFigs. 1 to 7 inclusive are formed male and female respectively bycrimping the top and bottom of the side 23 as indicated by the numeral29 in Figs. 4, 5 and 7 and by forming the side 24 with upper and lowerlaterally protuberant edges 35, the said sides 23 and 2d when so formedprovide means for accomplishing a tongue and groove joint betweenadjacent roof tiles when erected in lateral juxtaposition with respectto each other.

The tops 230 and 229 respectively of the sides 23 and 24 are preferablyturned inward as indicated in Figs. 4, 5 and 7 to provide protectionagainst breakage at the upper corners of the roof tile 20. An inwardlyand downwardly projecting strip 3i may be formed integral with the topof the sides 23 and 24 as indicated in Fig. ,4 onto which thereinforcing mesh 28 of the cementitious topping 27 may be welded at W,or, in order to disperse with welding and to provide suitable anchorageand means -for the accurate placement of the reinforcing mesh 28 of thecementitious topping 21, suitable arms 32 preferably having upwardlydisposed hooked lugs 33 formed on the ends thereof may be stamped andbent inward from the sides 23 and 2:2 to a position normal thereto asbest shown in Figs. 5, 6 and 7.

Although the insulation 25 is shown in the embodiment of the inventiondisclosed in Figs. l to 7 inclusive to be of cellular corrugated paperor cardboard which is preferably treated to avoid the absorption ofmoisttue from the cementitious material 27, any insulation material maybe substituted therefor providing the said insulation materialsubstituted is capable of repelling moisture at least for a timesumcient for the cementitious topping 2l to set and harden. If theinsulation 25 is not waterproof per se, it may be dipped in hot asphaltor the like to make the same water repellant during the setting of thecementitious material 27. A suitable mask 34 is preferably placed overthe ends of the corrugated paper or cardboard insulation 25 as indicatedin Fig. 3 to prevent the cementitious material 21@ from running in theends thereof prior to setting. If required, the said cementitiousmaterial 2l' and 2li] may be provided with Vsome sort of integralwaterproofing sufficient to make the said cementitious topping 2 andends 270 of the roof tile 25 water repellant or waterproof whereby toavoid any possibility of the said tile absorbing water from rain ormelting snow during shipment and ereck tion.

The sides of the said insulation 25 may be formed as indicated by thenumeral 35 in Fig. 7 by compressing the sides thereof from the topdownward and stapling the said sides in the compressed position by aplurality of staples 35, or otherwise if other than corrugated paperinsulation material is used, to'provide an additional mass ofcementitious material 2l alongside the sides 29 and 24 of the roof tileto aid in resisting vertical and horizontal shears in cases where theroof tile is used on long spans and when the said tile is subjected toheavy loading.

In the embodiment of the invention disclosed in Figs. l to 7 inclusiveit is obvious that the arrangement of the several parts of the compositeroof tile 25 is such .as will permit the metal base 22 to resist thetensile stresses of ilexure, will cause the metal sides 23 and 24 andthe cementitious material 21 adjacent thereto to resist the horizontaland vertical shearing stresses of the composite tile, and will cause thecementitious topping 2l reinforced by the mesh 28 or the like to resistnot only the compressive stresses of flexure of the composite rtile butwill prevent crushing of the insulation material 25 therein due to thefact that the said topping 21 spans laterally between the side 23 andthe side 24 of the said composite tile. Also, the tops 23B and 24U ofthe metal sides 23 and 24 aid the cementitious topping Z7 and thereinforcing mesh 28 in resisting compressive stresses of flexure of thecomposite ltile 20. In fact, all of the elements of the said compositeroof tile 2l! except the insulation 25 thereof act together as a unitarywhole to provide resistance against the flexural stresses to which thesaid tile may be subjected.

.The said insulation 25 being completely surrounded by the cementitiousmaterial 21 and 210 and the metal base 22 is completely protected fr-ommoisture during shipment and erection.

The composite roof tile 40 disclosed in Figs. 8 and 9 is similar in manyrespects to the composite roof tile 29 hereinbefore described and shownin Figs. 1 to '7y inclusive. Referring now particularly to Figs. 8 and9, the composite roof tile 40 is composed, in general, of a metal base4l with vertically disposed sides 42 preferably formed integraltherewith by being bent upwardly therefrom, a block of insulationmaterial 43 of a width equal to the distance between the said verticallydisposed sides 42 and of a length slightly shorter than the said metalbase 4| preferably supported in spaced relationship thereabove on aplurality of suitable ribs 44 formed in the said base 4I, a cementitioustopping 45 disposed solely above the said insulation 43 except at theends and as indicated by the numeral 459 in Fig. 9, and a mesh or othersuitable reinforcement 45 for the said topping 45 preferably supportedfrom the upper portion of the vertically disposed sides 42 in a mannersimilar to the construction shown in Fig. 8, however, the saidreinforcement 4E may be welded to the said vertically disposed sides 42in any desired manner, not shown, but as suggested in Fig. 4. The sides42 of the embodiment of the invention disclosed in Figs. 8 and 9 arepreferably formed to provide a longitudinally disposed slot 41 thereinfor receiving a spline 48 by means of which a joint between adjacentroof tiles vmay be accomplished during the erection of the said rooftiles 49 in lateral juxtaposition with respect to each other asindicated by the dot and dash lines 400 in Fig. 8.

I'he tops 420 of the sides 42 are preferably turned inward as indicatedin Fig. 8 to provide protection against breakage for the upper cornersof the roof tile 40.

In order to provide suitable anchorage and means for the accurateplacement of the reinforcing mesh 46 of the cementitious topping 45,suitable arms 49 preferably having upwardly disposed hooked lugs 50formed on the ends thereof may be stamped and bent inward from the sides42 to a position normal thereto as best indicated in Figs. 8 and 9.

Although the insulation 43 is shown in the embodiment of the inventiondisclosed in Figs. 8 and 9 to be of cellular corrugated paper orcardboard which is preferably treated to avoid the absorption ofmoisture from the cementitious material 45, any insulation material maybe substituted therefor providing the said insulation materialsubstituted is capable of repelling moisture at least for a timesufficient for the cementitious topping 45 to set and harden. If theinsulation 43 is not waterproof per se, it may be dipped in hot asphaltor the like to make the same water repellant during the setting of thecementitious material 45. A suitable mask 5l is preferably placed overthe end of the corrugated paper or cardboard insulation 43 as indicatedin Fig. 9 to prevent the cementitious material 459 from running in theend thereof prior to setting. If required, the said cementitiousmaterial 45 and 455 may be provided with some sort of' integralwaterproofing sufficient to make the said cementitious topping 45 andends 450 of the roof tile 45 water repellant or waterproof whereby toavoid any possibility of the said tile absorbing water from rain ormelting snow during shipment and erection. I v

In the embodiment of the invention disclosed in Figs. 8 and 9 it isobvious that the arrangement of the several parts of the composite rooftile are such las will permit th-e metal base 4l to resist the tensilestresses of flexure, will cause the metal sides 42 and the cementitiousmaterial 45 near the top thereof and adjacent thereto to f resist thehorizontal and vertical shearing stresses of the composite tile, andwill cause the cementitious topping 45 reinforced by the mesh 45 or thelike to resist not only the compressive stresses of iiexure of thevcomposite tile but will prevent crushing of the insulation material 43therein due to the fact that the said topp-ing 45 spans laterallybetween the vertically disposed sides 4E of the said composite tile, thesaid cementitious topping 45 being supported on that portion of the fvertically disposed sides 42 bent inwardly above the insulation material43 for providing the longitudinally disposed spline slots 47 ashereinbefor-e described. Also, the tops 425 of the metal sides 42 aidthe cementitious topping 45 and the reinforcing mesh 46 in resistingcompressive stresses of ilexure of the composite tile 40. In fact, allof the elements of the said composite roof tile 49 except the insulation43 thereof act together as a unitary whole to provide resistance againstthe flexural stresses to which the said tile may be subjected.

Still another embodiment of the invention is disclosed in Figs. 10 to 13inclusive wherein the composite roof tile 69 shown supported on the roofbeams or purlinsv 2| comprises, in general, a metal base 6I preferablyhaving a pair of longitudinally disposed laterally spaced depending ribs62 and a pair of adjacent longitudinally disposed central depending ribs53 formed to provide a central vertically disposed longitudina-lT-shapedV member 64, vertically disposed f sides t5 preferably formedintegral with the said metal base 6I by being bent upwardly fromthebottom of the said longitudinally disposed Vlaterally spaced dependingribs 62V of the said base 6I,

blocks of insulation material ireach of a widthequal to the distancebetween the said central ribs 63 and a vertically disposed side 65androf a length slightly shorter than the said metal base 6l preferablyplaced on the said metal base 6l equidistant from the ends thereof, acementitious topping 6l disposed solely above the said insulation 6Gexcept at the ends as indicated by the numeral Si@ in Fig. 12, and amesh or other suitable reinforcement i for the said topping 51preferably supported from and welded to the top of the said upwardlydisposed central T-shaped member' @it and the vertically disposedrsidesin a manner similar to the construction shown` in Fig. 13the position ofthe weld being' indicated by the letter W in the drawings.

The two sides of the vertically disposed longitudinal T-shaped member 64are preferably welded together either continuously or at suitableintervals as indicated by the character W-l in Fig. 12. The said weldW-l increases the lateral bending strength ofthe composite roof tileSii.

The sides $5 of the embodiment of the invention disclosed in Figs. 1G to13 inclusive are preferably formed tc providea longitudinally -disposedslot 69 therein for receiving a spline 'l0 by means of which a jointbetween adjacent roof tiles may b-e accomplished during the erection ofthe said roof tiles t@ in lateral juxtaposition with respect to eachother.

The tops 55@ of the sides t5 are preferably turned inward as indicatedin Fig. 8 to provide protection against breakage at the upper cor.

ners of the roof tile tt.

The insulation G in the embodiment of the invention disclosed in Figs.10 to 13 inclusive may be of any suitable cellular or fibrous materialand is preferably dipped in a hot .asphalt or other suitablewaterproofing material to provide a moisture proof coating iltherearound. It is readily observed that if a hot asphalt coating 'li isused around the insulation 56 the said insulation 66 becomes cementedthereby to the metal base El, the sides t5 and the T-shaped verticallydisposed central member Si whereupon moisture from the cementitioustopping tl is repelled from the said insulation material @t prior to andafter the said cementitious topping 6l has set and hardened. Likewise,moisture from or through the cementitious ends Stil is prevented fromentering the endof the said insulation material Sii. It is preferablethat if the cementitious material 5l and Sie is not waterproof per se,that some sort of suitable integral waterprooiing may be provided tomake the said cementitious topping 6l and ends 5l@ of the roof tile 6dWater repellant or waterproof whereby to avoid any possibility of thesaid roof tile dit absorbing water from rain or melting snow duringshipment and erection.

In the embodiment of the invention disclosedv in Figs. 1G to i3inclusive it is obvious that the arrangement of the several parts of thecomposite roof tile @dare such as will permit the metal base Si toresist the tensile stresses of flexure, will cause the metal sides 5 andthe cementitious material Gl n-ear the top thereof and adjacent theretoto resist the horizontal and vertical shearing stresses of the saidcomposite tile, and

will cause: the cementitious. topping 6l reinforced bythe mesh 68 or thelike to resist not only the compressive stresses of flexure of' thecomposite tile G9 but will prevent crushing of the insulation materialG5 therein due to the fact that the said topping 6l stands laterallybetween the vertically disposed sides 65 of the said composite tile, thesaid cementitious topping 45 being supported on that portion of the.vertically disposed sides 65 bent inwardly above the insulation material6G for providing the longitudinally disposed spline slots t9 ashereinbefore described. Also,the central longitudinally disposedT-shaped member Bt together withthe reinforcing mesh 38 welded thereto`provide the necessary horizon tal and vertical shear resistance topermit the central-depending ribs E3 andcementitious topping 51 torresist the tensile and compressive stresses of lexure at thelongitudinal central portion of the said roof' tile B0. Also, thetops650 of-the metal sides S5 aid the cementitious toppingi tl' and thereinforcing mesh SS in resisting compressive stresses of the compositeroo-f tile Gil atv the sides thereof. In fact, all ofthe elements of'the said composite roof tile 5G except the insulation (it thereof acttogether as a unitary Whole. to provide resistance against the flexural.

stresses to which the said roof tile @il may be subjected.

It is obvious that the applicant herein has provided either in theembodiment of the invention disclosed in Figs. l to 'l inclusive, theembodiment of the invention disclosed in Figs. 8 and 9 or in theembodiment of the invention disclosed in Figs. 10 to 13 inclusive acomplete unitary factory fabricated composite insulation carrying rooftile in which the metal base and sides and topping of cementitiousmaterial are suitably bonded together and are caused to act together asa unitary whole in resisting flexural stresses, and has provided acomposite roof tile which carries its own insulation and which iscapable of'being,

stored and Verected in all types of weather Without harmful eiects tothe insulation thereof, and has provided a roof tile which is capable ofsupplying the existing demand for a rooiing'unit which ris both strongand light, which carries its own insulation, which may be economicallymanufactured in large quantities, which is substantially free frombreakage during shipping', handling and erection, and which provides are safe insulated roong construction capable of being along the top ofthe said-.metal sides, insulation shallower than the said building unitdisposed between the said metal sides', a cementitious top' ping overthe said insulation, and reinforcement for the said cementitious toppingadapted to cause the said cementitious topping and metal portions ofthebuilding unit to act together as a unitary whole in resisting flexuralstresses.

2l A pre-fabricated structural building unit comprising a metal baseandmetal sides.- insulation within said building unit, .a'cementitioustopping over the said insulation, and reinforcement for saidcementitious topping anchored to the metal sides whereby to cause theentire building unit except the said insulation to act as a unitarywhole in resistingflexural stresses.

3. A pre-fabricated structural building unit comprising a metal base andmetal sides, inturned flanges along the top of the said metal sides,insulation within said building unit, a cementitious topping over thesaid insulation, and reinforcement for the said cementitious toppinganchored to the said inturned ilanges whereby to cause the entirebuilding unit except the said insulation to act as a unitary whole inresisting flexural stresses.

4. A pre-fabricated structural building unit comprising a metal base,metal sides formed upwardly from the said metal base, inturned flangesalong the top of the said metal sides, insulation shallower than thesaid building unit disposed between the said metal sides, ribs formed inthe said metal base adapted to support the said insulation in spacedrelationship above the said metal base and provide a plurality of airspaces between the said insulation and the said metal base, and areinforced cementitious topping over the said insulation.

5. A pre-fabricated structural building unit comprising a metal base,metal sides formed upwardly from the said metal base, inturned flangesalong the top of the said metal sides; insulation shallower, shorter andnarrower than the said building unit disposed in spaced relationshipbetween the said metal sides and inwardly with respect to the ends ofthe said metal base and sides; ribs formed in the said metal baseadapted to support the said insulation in spaced relationship above thesaid metal base and provide a plurality of air spaces between the saidinsulation and the said metal base, a reinforced cementitious toppingover the said insulation, and cementitious material extending across theends and along the sides of the said insulation within the length of thesaid building unit.

6. A pre-fabricated structural building unit 'comprising a metal baseand metal sides, insulation within said building unit, ribs formed inthe said metal base adapted to support the said insulation in spacedrelationship above the said metal base and provide a plurality of airspaces between the said insulation and the said metal base, acementitious topping over the said insulation, and reinforcement forsaid cementitious topping anchored to the metal sides whereby to causethe entire building unit except the said insulation to act as a unitarywhole in resisting iiexural stresses.

7. A pre-fabricated structural building unit comprising a metal base andmetal sides, inturned iianges along the top of the said metal sides,insulation within said building unit, ribs formed in the said metal baseadapted to support the said insulation in spaced relationship above thesaid metal base and provide a plurality of air spaces between the saidinsulation and the said metal base, a cementitious topping over the saidinsulation, and reinforcement for the said cementitious topping anchoredto the said inturned flanges whereby to cause the entire building unitexcept the said insulation to act as a unitary whole in resistingilexural stresses.

8. A pre-fabricated structural building unit comprising a' metal baseand metal sides, insulation within said building unit, a centitioustopping over the said insulation, and reinforcement whereby to preventabsorption of moisture thereby during the setting of the saidcementitious material.

9. A pre-fabricated structural building unit comprising a metal base,metal sides formed upwardly from the said metal base, inturned flangesalong the top of the said metal sides, insulation shallower than thesaid building unit disposed between the said metal sides, a reinforcedcementitious topping over the said insulation, and means for makingthesaid insulation water repellant whereby to prevent the absorption ofmoisture thereby during the setting of the said cementitious material.

1D. A pre-fabricated structural building unit comprising a metal baseand metal sides, insulation within said building unit, a cementitioustopping over the said insulation, reinforcement for said cementitioustopping anchored to the metal sides whereby to cause the entire buildingunit except the said insulation to act as a unitary whole in resistingflexural stresses, and means for making the said insulation waterrepellant whereby to prevent the absorption of moisture thereby duringthe setting of the said cementitious material.

11. A pre-fabricated structural building unit comprising a metal baseand metal sides, an upwardly disposed longitudinal central rib formed inthe said metal base, insulation within the said building unit disposedbetween the sides and upwardly disposed central rib thereof, acementitious topping over the said insulation, and reinforcement forsaid cementitious topping anchored to the said metal sides and upwardlydisposed central rib whereby to cause the entire building unit exceptthe insulation to act as a unitary whole in resisting iiexural stresses.

12. A pre-fabricated structural building unit comprising a metal baseand metal sides, a pair of central and a pair of outer longitudinal ribsformed in the said metal base depending therebelow, an upwardly disposedlongitudinal central rib formed in the said metal base, insulationwithin the said building unit disposed beu tween the sides and upwardlydisposed central rib thereof, a cementitious topping over the saidinsulation, and reinforcement for said cementitious topping anchored tothe said metal sides and upwardly disposed central rib whereby to causethe entire building unit except the insulation to act as a unitary wholein resisting flexural stresses.

13. A pre-fabricated structural building unit comprising a metal baseand metal sides, an upwardly disposed longitudinal central rib formed inthe said metal base, insulation within the said building unit disposedbetween the sides and upwardly disposed central rib thereof, acementitious topping over the said insulation, reinforcement for saidcementitious topping anchored to the said metal sides and upwardlydisposed central rib whereby to cause the entire building unit exceptthe insulation to act as a unitary whole in resisting flexural stresses,and means for making the said insulation water repellant whereby toprevent absorption of moisture thereby during the setting of the saidcementitious material.

14. A pre-fabricated structural building unit comprising a metal baseand metal sides, a pair of central and a pair `of outer longitudinalvribs formed in the said metal base depending therebelow, an 4upwardlydisposed longitudinalcentral rib formed in the said metal base,insulation within the said building unit disposed betweenthe sides andupwardly disposed central rib thereof, a cementitious topping over thesaid insulation, reinforcement for said cernentitious topping anchoredto the said metal sides and upwardly'disposed central rib whereby tocause the entire building unit except the insulation to act as a unitarywhole in resisting exural stresses, and means for making the saidinsulation water repellant whereby to preventfabsorption of moisturethereby during the setting of the said cementitious material.

15. A pre-fabricated structural building unit comprising a metal baseand metal sides formed to provide a tongue and grooved joint betweenadjacent building units when juxtaposed, insulation within the saidbuilding unit, a cementitious topping over the `said insulation,reinforcement in said cementitious topping anchored to the -saidmetalsides whereby to cause the said building unit except the saidinsulation to act as aunitary whole in resisting flexural stresses.

16. In combination, a plurality of pre-fabricated structural buildingunits juxtaposed with respect to each other each of the said buildingunits composed of av metal base and metal sides crimped to provideinwardly disposed longitudinally extending grooves therein near the `topthereof, insulation within the said building unit, a topping ofcementitious material over the said insulation, reinforcement in thesaid cementitious topping welded to the said crimps in the metal sideswhereby to cause the entire building unit except the insulation thereofto act together Vas a unitary whole in resisting flexural stresses;

a metal spline frictionally disposed in adjacent longitudinal extendinggrooves of juxtaposed building units whereby to provide a tight jointtherebetween and cause the juxtaposed building units to act togetherwhile resisting the stresses of flexure.

ROY A. PLUMB.

